I have since covered the top with a nylon stocking (or covered the lid, actually). I haven't tried the hydei flies as my culture hadn't really matured yet. I had tried turkish gliders at first and they seem to quickly climb the sides and hang out on the bottom of the covered lid. I put half a grape in and did find by the morning a few were on the grape.

The D. melanogaster wingless flies so far are working the best. They don't seem to climb the sides much and stay longer on the substrate.

I have also since gotten another little baby tomato frog about the same size and they seem to be ok together and pretty much stay in the same hideout. The newer one is a slightly more orange color. When feeding them the other night the fruit flies got in the water container and the new one found them and started feasting. I have a short video of them feeding.

They are feisty little frogs. Even at their size if I touch them, they puff up! They both are doing well, chunky little babies, and I enjoy watching them when I get the chance in the evening, especially at feeding time.